The present invention relates to a composite, particularly one that can be used in ballistic resistant articles, which includes a network of high strength fibers in a vinyl ester matrix material.
Various constructions are known for ballistic resistant composites used in ballistic resistant articles such as helmets, panels, and vests. These composites display varying degrees of resistance to penetration by high speed impact from projectiles such as BB's, bullets, shells, shrapnel, glass fragments and the like. U.S. Pat. Nos. 5,196,252; 5,187,023; 5,185,195; 5,175,040; 5,167,876; 5,165,989; 5,124,195; 5,112,667; 5,061,545; 5,006,390; 4,953,234; 4,916,000; 4,883,700; 4,820,568; 4,748,064; 4,737,402; 4,737,401; 4,681,792; 4,650,710; 4,623,574; 4,613,535; 4,584,347; 4,563,392; 4,543,286; 4,501,856; 4,457,985; and 4,403,012 and PCT Publication No. WO 91/12136 describe ballistic resistant composites which include high strength fibers made from materials such as extended chain ultra-high molecular weight polyethylene.
Typically these fibers are coated, embedded or impregnated in a polymeric matrix material. During production of such composites the matrix materials must be dissolved in a solvent so that they are in a liquid form for application to the high strength fibers. The solvent then must be removed, usually by drying, in order to fabricate the composite.
Of particular interest among the above disclosures is the description of the materials that can be used for the matrix material that is found in PCT Publication No. WO 91/12136; column 14, lines 12-36, of U.S. Pat. No. 5,167,876; column 12, lines 25-39 of U.S. Pat. No. 4,820,568; and column 3, lines 1-5 and Example 1 of U.S. Pat. No. 5,165,989. These disclosures describe the use of a vinyl ester as the matrix material. This vinyl ester matrix material is the condensation product of epoxide resins and unsaturated acids that is diluted in a compound having double bond unsaturation such as a vinyl aromatic monomer as for example styrene, vinyl toluene and diallyl phthalate. A problem with these vinyl ester matrix materials is that the required unsaturated solvents have a high boiling point, thus necessitating more energy and time for removal of the solvent. A further problem with many of the organic solvents is that they require strict handling and disposal procedures because of potential environmental or health hazards.
A need exists, therefore, for vinyl ester matrix materials which do not require such troublesome solvents, but which provide adequate levels of ballistic performance, mechanical performance and chemical resistance.